Method of using films having optimized optical properties for chemical mechanical polishing endpoint detection

ABSTRACT

A method of using films having optimized optical properties for chemical mechanical polishing (CMP) endpoint detection. Specifically, one embodiment of the present invention includes a method for improving chemical mechanical polishing endpoint detection. The method comprises the step of depositing a dielectric layer over a reflectance stop layer. The reflectance stop layer is disposed above a component that is disposed on a semiconductor wafer. During a determination of the thickness of the dielectric layer using a reflected signal of light, the reflectance stop layer substantially reduces any light from reflecting off of the component. Therefore, the present invention provides a method and system that provides more accurate endpoint detection during a CMP process of semiconductor wafers. As a result of the present invention, an operator of a CMP machine knows precisely when to stop a CMP process of a semiconductor wafer. Furthermore, the present invention enables the operator of the CMP machine to know within a certain accuracy the film (e.g., dielectric layer) thickness remaining after the CMP process of the semiconductor wafer. Moreover, the present invention essentially eliminates excessive chemical mechanical polishing of the semiconductor wafer. As such, not as much dielectric material needs to be deposited on the wafer in order to compensate for excessive chemical mechanical polishing of the semiconductor wafer. Therefore, the present invention is able to reduce fabrication costs of semiconductor wafers.

TECHNICAL FIELD

[0001] The field of the present invention pertains to semiconductorfabrication processing. More particularly, the present invention relatesto the field of endpoint detection during chemical mechanical polishingof semiconductor wafers.

BACKGROUND ART

[0002] Most of the power and usefulness of today's digital integratedcircuit (IC) devices can be attributed to the increasing levels ofintegration. More and more components (resistors, diodes, transistors,and the like) are continually being integrated into the underlying chip,or IC. The starting material for typical ICs is very high puritysilicon. The material is grown as a single crystal and takes the shapeof a solid cylinder. This crystal is then sawed (like a loaf of bread)to produce wafers typically 10 to 30 cm in diameter and 250 micronsthick.

[0003] The geometry of the features of the IC components are commonlydefined photographically through a process known as photolithography.Very fine surface geometries can be reproduced accurately by thistechnique. The photolithography process is used to define componentregions and build up components one layer on top of another. Complex ICscan often have many different built up layers, each layer havingcomponents, each layer having differing interconnections, and each layerstacked on top of the previous layer. The resulting topography of thesecomplex IC's often resemble familiar terrestrial “mountain ranges,” withmany “hills” and “valleys” as the IC components are built up on theunderlying surface of the silicon wafer.

[0004] In the photolithography process, a mask image, or pattern,defining the various components, is focused onto a photosensitive layerusing incident light. The image is focused onto the surface using theoptical means of the photolithography tool, and is imprinted into thephotosensitive layer. To build ever smaller features, increasingly fineimages must be focused onto the surface of the photosensitive layer,i.e. optical resolution must increase. As optical resolution increases,the depth of focus of the mask image correspondingly narrows. This isdue to the narrow range in depth of focus imposed by the high numericalaperture lenses in the photolithography tool. This narrowing depth offocus is often the limiting factor in the degree of resolutionobtainable, and thus, the smallest components obtainable using thephotolithography tool. The extreme topography of complex ICs, the“hills” and “valleys,” exaggerate the effects of decreasing depth offocus. Thus, in order to properly focus the mask image definingsub-micron geometries onto the photosensitive layer, a precisely flatsurface is desired. The precisely flat (i.e., fully planarized) surfacewill allow for extremely small depths of focus, and in turn, allow thedefinition and subsequent fabrication of extremely small components.

[0005] Chemical mechanical polishing (CMP) is a preferred method ofobtaining full planarization of a semiconductor wafer. It involvesremoving a sacrificial layer of dielectric material using mechanicalcontact between the wafer and a moving polishing pad saturated withslurry. Polishing flattens out height differences, since high areas oftopography (hills) are removed faster than areas of low topography(valleys). Polishing is the only technique with the capability ofsmoothing out topography over millimeter scale planarization distancesleading to maximum angles of much less than one degree after polishing.

[0006]FIG. 1 is a top view of a chemical mechanical polishing (CMP)machine 100 and FIG. 2 is a side view of CMP machine 100. CMP machine100 is fed semiconductor wafers to be polished. CMP machine 100 picks upthe wafers with an arm 101 and places them onto a rotating polishing pad102. Polishing pad 102 is made of a resilient material and is textured,often with a plurality of predetermined grooves 103, to aid thepolishing process. Polishing pad 102 rotates on a platen 104, or turntable located beneath polishing pad 102, at a predetermined speed. Awafer 105 is held in place on polishing pad 102 within a carrier ring112 that is connected to a carrier film 106 of arm 101. The frontsurface of wafer 105 rests against polishing pad 102. The back surfaceof wafer 105 is against the lower surface of carrier film 106 of arm101. As polishing pad 102 rotates, arm 101 rotates wafer 105 at apredetermined rate. Arm 101 forces wafer 105 into polishing pad 102 witha predetermined amount of down force. CMP machine 100 also includes aslurry dispense arm 107 extending across the radius of polishing pad102, which dispenses a flow of slurry onto polishing pad 102.

[0007] The slurry is a mixture of deionized water and polishing agentsdesigned to chemically aid the smooth and predictable planarization ofwafer 105. The rotating action of both polishing pad 102 and wafer 105,in conjunction with the polishing action of the slurry, combine toplanarize, or polish, wafer 105 at some nominal rate. This rate isreferred to as the removal rate. A constant and predictable removal rateis important to the uniformity and throughput performance of the waferfabrication process. The removal rate should be expedient, yet yieldprecisely planarized wafers, free from surface anomalies. If the removalrate is too slow, the number of planarized wafers produced in a givenperiod of time decreases, hurting wafer throughput of the fabricationprocess. If the removal rate is too fast, the CMP planarization processwill not be consistent across several wafers in a batch, thereby hurtingthe consistency of the fabrication process.

[0008] To aid in maintaining a stable removal rate, CMP machine 100includes a conditioner assembly 120. Conditioner assembly 120 includes aconditioner arm 108, which extends across the radius of polishing pad102. An end effector 109 is connected to conditioner arm 108. Endeffector 109 includes an abrasive conditioning disk 110 which is used toroughen the surface of polishing pad 102. Conditioning disk 110 isrotated by conditioner arm 108 and is translationally moved towards thecenter of the polishing pad 102 and away from the center of polishingpad 102, such that conditioning disk 110 covers the radius of polishingpad 102. In so doing, conditioning disk 110 covers the surface area ofpolishing pad 102, as polishing pad 102 rotates. A polishing pad havinga roughened surface has an increased number of micro-pits and gouges inits surface from conditioner assembly 120 and therefore produces afaster removal rate via increased slurry transfer to the surface ofwafer 105. Without conditioning, the surface of polishing pad 102 issmoothed during the polishing process and removal rate decreasesdramatically. Conditioner assembly 120 re-roughens the surface ofpolishing pad 102, thereby improving the transport of slurry andimproving the removal rate.

[0009] As described above, the CMP process uses an abrasive slurry on apolishing pad. The polishing action of the slurry is comprised of anabrasive frictional component and a chemical component. The abrasivefrictional component is due to the friction between the surface of thepolishing pad, the surface of the wafer, and abrasive particlessuspended in the slurry. The chemical component is due to the presencein the slurry of polishing agents which chemically interact with thematerial of the dielectric layer of wafer 105. The chemical component ofthe slurry is used to soften the surface of the dielectric layer to bepolished, while the frictional component removes material from thesurface of wafer 105.

[0010] Referring still to FIGS. 1 and 2, the polishing action of theslurry determines the removal rate and removal rate uniformity, andthus, the effectiveness of the CMP process. As slurry is “consumed” inthe polishing process, the transport of fresh slurry to the surface ofwafer 105 and the removal of polishing by-products away from the surfaceof wafer 105 becomes very important in maintaining the removal rate.Slurry transport is facilitated by the texture of the surface ofpolishing pad 102. This texture is comprised of both predefined grooves103 and micro-pits that are manufactured into the surface of polishingpad 102 and the inherently rough surface of the material from whichpolishing pad 102 is made.

[0011] The slurry is transported by grooves 103 and micro-pits ofpolishing pad 102 under the edges of wafer 105 as both polishing pad 102and wafer 105 rotate. Consumed slurry and polishing by-products, in asimilar manner, are also transported by grooves 103 and micro-pits ofpolishing pad 102 away from the surface of wafer 105. As the polishingprocess continues, fresh slurry is continually dispensed onto polishingpad 102 from slurry dispense arm 107. The polishing process continuesuntil wafer 105 is sufficiently planarized and removed from polishingpad 102.

[0012] There are several conventional prior art techniques to determinewhen to remove wafer 105 from polishing pad 102 of CMP machine 100. Onesuch technique is referred to as endpoint detection, which is a way ofdetermining when to stop the CMP process of a semiconductor wafer. Onetype of prior art endpoint detection technique, which is well known bythose of ordinary skill in the art, involves using reflected incidentlight to determine the thickness of a film (e.g., oxide) on wafer 105during the CMP process. Once the film achieves a desired thickness, theCMP process is discontinued.

[0013] Specifically, this prior art endpoint detection techniquetypically includes a transparent window slit 114 of FIG. 1 that islocated within polishing pad 102 and enables incident light to passthrough it. Furthermore, window slit 114 is positioned within polishingpad 102 such that wafer 105 passes over it every time polishing pad 102makes a complete rotation. In other words, every time polishing pad 102rotates during the CMP process, window slit 114 passes underneath wafer105. As wafer 105 passes over window slit 114, incident light shinesthrough window slit 114 and reflects off of different surfaces withinwafer 105. As such, a single wavelength or different wavelengths ofreflected incident light are then used to determine the thickness of afilm on wafer 105 during the CMP process. As mentioned above, once thefilm achieves a desired thickness, the CMP process of wafer 105 isdiscontinued.

[0014] There are disadvantages associated with the prior art endpointdetection technique described above. One of the main disadvantages isthat it does not provide accurate endpoint detection during a CMPprocess of semiconductor waters. One of the factors that causes theprior art light reflection endpoint detection technique to be inaccurateis referred to as “pattern density effects.” For example, FIG. 3 showsincident light rays 302-308 reflecting off of different surfaces withina side sectional view of semiconductor wafer 105. Since incident lightrays 302-308 each reflect off of different surfaces at different depthswithin wafer 105, a subsequent film thickness determination of anyparticular layer using reflected incident light rays 302-308 isdifficult. This is referred to as pattern density effects. As such,determining when the desired endpoint has been reached during the CMPprocess of wafer 105 becomes more difficult and therefore results inless control of the film removal process.

[0015] Another factor that causes the prior art light reflectionendpoint detection technique to provide inaccurate endpoint detectionduring a CMP process of semiconductor wafers is that it is difficult toprecisely align window slit 114 of FIG. 1 with a particular desirableregion of semiconductor wafer 105. One of the reasons for thisdifficulty is that polishing pad 102 is rotating at the same time arm101 rotates wafer 105 at a predetermined rate. As a result of thisalignment difficulty, the reflected incident light rays 302-308 of FIG.3 also represent what would be typically received from wafer 105 duringa film thickness determination of any particular layer. As such, thereceived reflected incident light rays 302-308 make it difficult todetermine the film thickness of any particular layer thereby reducingthe accuracy at which the desired endpoint can be detected. Therefore,the prior art endpoint detection technique described above isundesirable because it does not provide accurate endpoint detectionduring a CMP process of semiconductor wafers.

[0016] Accordingly, a need exists for a method and system that providesmore accurate endpoint detection during a CMP process of semiconductorwafers.

DISCLOSURE OF THE INVENTION

[0017] The present invention provides a method and system that providesmore accurate endpoint detection during a chemical mechanical polishing(CMP) process of semiconductor wafers. As a result of the presentinvention, an operator of a CMP machine knows precisely when to stop aCMP process of a semiconductor wafer. Furthermore, the present inventionenables the operator of the CMP machine to know within a certainaccuracy the film (e.g., dielectric layer) thickness remaining after theCMP process of the semiconductor wafer. Moreover, the present inventionessentially eliminates excessive chemical mechanical polishing of thesemiconductor wafer. As such, not as much dielectric material needs tobe deposited on the wafer in order to compensate for excessive chemicalmechanical polishing of the semiconductor wafer. Therefore, the presentinvention is able to reduce fabrication costs of semiconductor wafers.

[0018] Specifically, one embodiment of the present invention includes amethod for improving chemical mechanical polishing endpoint detection.The method comprises the step of depositing a dielectric layer over areflectance stop layer. The reflectance stop layer is disposed above acomponent that is disposed on a semiconductor wafer. During adetermination of the thickness of the dielectric layer using a reflectedsignal of light, the reflectance stop layer substantially reduces anylight from reflecting off of the component.

[0019] Another embodiment of the present invention also includes amethod for improving chemical mechanical polishing endpoint detection.The method comprises the step of depositing a reflectance stop layerabove a component that is disposed on a semiconductor wafer. Thereflectance stop layer substantially reduces any light from reflectingoff of the component. The method also includes the step of depositing adielectric layer over the reflectance stop layer and the component.Another step of the method includes removing material from thedielectric layer disposed above the semiconductor wafer using a chemicalmechanical polishing process. Moreover, the method further includes thestep of determining the thickness of the dielectric layer disposed abovethe semiconductor wafer using a reflected signal of light. In responseto the dielectric layer substantially achieving a desired thickness, themethod includes the step of stopping the chemical mechanical polishingprocess of the semiconductor wafer.

[0020] In still another embodiment, the present invention comprises thestep of depositing a first dielectric layer above a reflectance stoplayer. The reflectance stop layer is disposed above a second dielectriclayer. The second dielectric layer is disposed over a component that isdisposed on a semiconductor wafer. During a determination of thethickness of said second dielectric layer above said component using areflected signal of light, the reflectance stop layer substantiallyreduces any light from reflecting off of other surfaces except saidcomponent.

[0021] Another embodiment of the present invention comprises the step ofdepositing a first dielectric layer over a component disposed on asemiconductor wafer. The method includes the step of depositing areflectance stop layer above the first dielectric layer. Furthermore,the method includes the step of depositing a second dielectric layerabove the reflectance stop layer. Another step of the method includesremoving material from the second dielectric layer and the reflectancestop layer disposed above the semiconductor wafer using a chemicalmechanical polishing process. The second dielectric layer and thereflectance stop layer subsequently are substantially removed from abovethe component. Moreover, the method further includes the step ofdetermining the thickness of the first dielectric layer above thecomponent using a reflected signal of light. The reflectance stop layerthat remains substantially reduces any light from reflecting off ofother surfaces except the component. In response to the first dielectriclayer substantially achieving a desired thickness above the component,the method includes the step of stopping the chemical mechanicalpolishing process of the semiconductor wafer.

[0022] These and other advantages of the present invention will no doubtbecome obvious to those of ordinary skill in the art after having readthe following detailed description of the preferred embodiments whichare illustrated in the drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are incorporated in and form apart of this specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention:

[0024] Prior Art FIG. 1 is a top view of a prior art chemical mechanicalpolishing machine.

[0025] Prior Art FIG. 2 is a side view of the prior art chemicalmechanical polishing machine of FIG. 1.

[0026] Prior Art FIG. 3 shows incident light reflecting off of a sidesectional view of a semiconductor wafer in order to determine thethickness of its films during a chemical mechanical polishing process.

[0027]FIG. 4A is a top view of a chemical mechanical polishing machinein accordance with one embodiment of the present invention.

[0028]FIG. 4B is a side view of the chemical mechanical polishingmachine of FIG. 4A.

[0029]FIG. 5A is a side sectional view of a semiconductor wafer having areflectance stop layer deposited above metal components in accordancewith one embodiment of the present invention.

[0030]FIG. 5B shows incident light reflecting off of the semiconductorwafer of FIG. 5A in order to determine the thickness of its films duringa chemical technical polishing process.

[0031]FIG. 6A is a side sectional view of a semiconductor wafer having areflectance stop layer deposited between two dielectric layers inaccordance with one embodiment of the present invention.

[0032]FIG. 6B shows incident light reflecting off of the semiconductorwafer of FIG. 6A in order to determine the thickness of its films duringa chemical mechanical polishing process.

[0033]FIG. 7 is a flowchart of a method in accordance with oneembodiment of the present invention for improving chemical mechanicalpolishing endpoint detection during planarization of semiconductorwafers.

[0034]FIG. 8 is a flowchart of a method in accordance with anotherembodiment of the present invention for improving chemical mechanicalpolishing endpoint detection during planarization of semiconductorwafers.

[0035] The drawings referred to in this description should be understoodas not being drawn to scale except if specifically noted.

BEST MODE FOR CARRYING OUT THE INVENTION

[0036] Reference will now be made in detail to the preferred embodimentsof the invention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction with thepreferred embodiments, it will be understood that they are not intendedto limit the invention to these embodiments. On the contrary, theinvention is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of theinvention as defined by the appended claims. Furthermore, in thefollowing detail description of the present invention, numerous specificdetails are set forth in order to provide a thorough understanding ofthe present invention. However, it will be obvious to one of ordinaryskill in the art that the present invention may be practiced withoutthese specific details. In other instances, well known methods,procedures, components, and circuits have not been described in detailas not to unnecessarily obscure aspects of the present invention.

[0037] Chemical mechanical polishing (CMP) is a preferred method ofobtaining full planarization of a semiconductor wafer containing devicesfor fabrication processing. The CMP process involves removing all, or aportion of, a layer of dielectric material using mechanical contactbetween the wafer and a moving polishing pad saturated with a polishingslurry. Polishing through the CMP process flattens out heightdifferences, since high areas of topography (hills) are removed fasterthan areas of low topography (valleys). The CMP process has thecapability of smoothing out topography over millimeter scaleplanarization distances, leading to maximum angles of much less than onedegree after polishing.

[0038] Furthermore, chemical mechanical polishing is widely accepted asa preferred intermediary process during fabrication of complexintegrated circuits (ICs) having multiple layers. For instance, complexICs often have many different built up layers, each layer havingcomponents, each layer having differing interconnections, and each layerfabricated on top of the previous layer. One of the techniques forfabricating the individual layers of complex ICs is to encase the metalcomponents of each layer within dielectric material, commonly referredto as an inter-metal dielectric layer. The purpose of the inter-metaldielectric layer is to electrically isolate the metal components of onelayer from the metal components of previous and/or subsequent layers.Once an inter-metal dielectric layer is fabricated, another layer ofcomponents is subsequently fabricated on top of it. But before thesubsequent layer of components are fabricated, it is important to firstplanarize the dielectric surface onto which they will be fabricated inpreparation for the photolithography process, previously describedabove. Typically, chemical mechanical polishing is the preferredintermediary process used to planarize the dielectric surface beforefabrication of a subsequent layer of components.

[0039] It is appreciated that there are different techniques fordetermining when to stop a CMP process of a semiconductor wafer, whichis commonly referred to as endpoint detection. The present inventionprovides a method and system that provides more accurate endpointdetection during a chemical mechanical polishing process ofsemiconductor wafers. One embodiment of the present invention includesthe implementation of the endpoint detection technique of usingreflected incident light to determine the thickness of a film (e.g.,oxide) on a semiconductor wafer during a CMP process, as describedabove. As a result of the present invention, an operator of a CMPmachine knows precisely when to stop a CMP process of a semiconductorwafer. Furthermore, the present invention enables the operator of theCMP machine to know within a certain accuracy the film (e.g., dielectriclayer) thickness remaining after the CMP process of the semiconductorwafer. Moreover, the present invention essentially eliminates excessivechemical mechanical polishing of the semiconductor wafer. As such, notas much dielectric material needs to be deposited on the wafer in orderto compensate for excessive chemical mechanical polishing of thesemiconductor wafer. Therefore, the present invention is able to reducefabrication costs of semiconductor wafers. The CMP endpoint detectionmethod of the present invention and its benefits are described ingreater detail below.

[0040]FIG. 4A shows a top view of a chemical mechanical polishing (CMP)machine 400 in accordance with one embodiment of the present inventionutilized for chemical mechanical polishing of semiconductor wafers. FIG.4B shows a side view of CMP machine 400. CMP machine 400 picks up asemiconductor wafer 410, which was fabricated in accordance with anembodiment of the present invention, with an arm 402 and places it ontothe rotating polishing pad 404. Polishing pad 404 is made of a resilientmaterial and is textured typically with a plurality of grooves 406 toaid the polishing process. Polishing pad 404 of CMP machine 400 rotatesat a predetermined speed on a platen 408, or turn table located beneathpolishing pad 404. Arm 402 forces wafer 410 into polishing pad 404 witha predetermined amount of down force. Wafer 410 is held in place on thepolishing pad 404 by a carrier ring 412 and a carrier film 414 of arm402. The front surface of wafer 410 rests against the polishing pad 404while the back surface of wafer 410 is against the lower surface ofcarrier film 414 of arm 402. As polishing pad 404 rotates, arm 402 alsorotates wafer 410 at a predetermined rate.

[0041] CMP machine 400 also includes a slurry dispense arm 416 extendingacross the radius of polishing pad 404. Slurry dispense arm 416dispenses a flow of slurry onto polishing pad 404. CMP machine 400further includes a conditioner assembly 418 which consists of an endeffector 420 and a conditioner arm 422 that extends across the radius ofpolishing pad 404. End effector 420 is connected to conditioner arm 422and includes an abrasive disk 424 that is used to roughen the surface ofthe polishing pad 404, in the manner described above. The dispensedslurry is transported by grooves 406 and micro-pits of polishing pad 404under the edges of wafer 410 as both polishing pad 404 and wafer 404rotate. Consumed slurry and polishing by-products, in a similar manner,are also transported by grooves 406 and micro-pits of polishing pad 404away from the surface of wafer 410. As the polishing process continues,fresh slurry is continually dispensed onto polishing pad 404 from slurrydispense arm 416. The polishing process of wafer 410 continues until itsdesired endpoint is detected. Once the endpoint is detected, the CMPprocess of wafer 410 is discontinued.

[0042] The endpoint detection technique implemented within the presentembodiment involves using reflected incident light to determine thethickness of a film (e.g., dielectric) on wafer 410 during the CMPprocess. Once the film achieves a desired thickness, the CMP process issuspended. This endpoint detection technique is well known by those ofordinary skill in the art. Specifically, the endpoint detectiontechnique implemented within the present embodiment includes atransparent window slit 426 of FIG. 4A that is located within polishingpad 404 and enables incident light to pass through it. Furthermore,window slit 426 is positioned within polishing pad 404 such that wafer410 passes over it every time polishing pad 404 makes a completerotation. That is, every time polishing pad 404 rotates during the CMPprocess, window slit 426 passes underneath wafer 410. As wafer 410passes over window slit 426, incident light shines through window slit426 and reflects off of different surfaces within wafer 410. As such, asingle wavelength or different wavelengths of reflected incident lightare then used to determine the thickness of the film on wafer 410 duringthe CMP process. Once the film achieves a desired thickness, the CMPprocess of wafer 410 is ended.

DETAILED DESCRIPTION OF THE STRUCTURE OF THE PRESENT INVENTION

[0043] With reference now to FIG. 5A, which is a side sectional view ofsemiconductor wafer 410 having reflectance stop layers 508 and 510located above components 504 and 506, respectively, in accordance withone embodiment of the present invention. Furthermore, a dielectric layer512 is deposited over reflectance stop layers 508 and 510, components504 and 506, and substrate 502 of semiconductor wafer 410. It should beappreciated that other embodiments of dielectric layer 512, inaccordance with the present embodiment, include any type ofnon-conductive material (e.g., oxide, polymer, and the like).Furthermore, it should also be appreciated that embodiments ofreflectance stop layers 508 and 510, in accordance with the presentembodiment, include silicon oxy-nitride, amorphous silicon, and thelike. Moreover, it should also be appreciated that embodiments ofcomponents 504 and 506, in accordance with the present embodiment,include any type of conductive material (e.g., aluminum, copper, silver,gold, and the like). After fabrication of semiconductor wafer 410,dielectric layer 512 is ready to be planarized to a desired thicknessusing CMP machine 400 of FIGS. 4A and 4B and the endpoint detectiontechnique described above.

[0044] Referring now to FIG. 5B, which shows a determination of thethickness of dielectric layer 512 using incident light (e.g., incidentlight rays 514-518) during a CMP process of semiconductor wafer 410.Within the present embodiment, it is appreciated that an amount ofdielectric layer 512 has been removed during the CMP process. It shouldbe further appreciated that the main purpose of reflectance stop layers508 and 510, within the present embodiment, is to suppress incidentlight from reflecting off of underlying components 504 and 508. As such,reflected incident light is substantially obtained from substrate 502.As a result, any changes in the reflectance of incident light during theCMP process is merely attributed to a change in the thickness ofdielectric layer 512. Therefore, by providing a more accuratemeasurement of the thickness of dielectric layer 512, the presentembodiment provides more accurate endpoint detection during the CMPprocess.

[0045] Specifically, as CMP machine 400 polishes dielectric layer 512 ofwafer 410, as described above, transparent window slit 426 passesunderneath wafer 410. As such, incident light rays 514-518 pass throughwindow slit 426 and shine on wafer 410 as shown in FIG. 5B. As a result,incident light rays 514 and 516 pass through dielectric layer 512 andare subsequently absorbed by reflectance stop layers 504 and 508,respectively. However, incident light ray 518 passes through dielectriclayer 512, reflects off of substrate 502, and subsequently passesthrough dielectric layer 512 to eventually be used to determine thethickness of dielectric layer 512. Therefore, the present embodimentlimits what incident light rays 51418 518 reflect off of within wafer410.

[0046] It should be appreciated that the if reflectance stop layers 508and 510 are deposited too thin above components 504 and 506, they willnot sufficiently suppress the reflection of incident light in the courseof a determination of the thickness of dielectric layer 512 during a CMPprocess. As such, it is important that a proper thickness of reflectancestop layers 508 and 510 are deposited above components 504 and 506,within the present embodiment. As such, the following examplesillustrates this point. Given the wavelength of incident light to beused to determine the thickness of dielectric layer 512 is 450nanometers (nm). Furthermore, reflectance stop layers 508 and 510 are anamorphous silicon having an absorption coefficient of about 4×10⁵/cm.Therefore, if 500 angstroms of reflectance stop layers 508 and 510 aredeposited above components 504 and 506, reflectance stop layers 508 and510 each provide 87% absorption of that particular wavelength ofincident light. Moreover, if 1000 angstroms of reflectance stop layers508 and 510 are deposited above components 504 and 506, reflectance stoplayers 508 and 510 each provide 98% absorption of that particularwavelength of incident light. Within the present embodiment, it shouldbe appreciated that reflectance stop layers 508 and 510 are not limitedto these specific examples of thickness.

[0047] With reference now to FIG. 6A, which is a side sectional view ofa semiconductor wafer 600 which is an alternate embodiment of thepresent invention. Specifically, semiconductor wafer 600 includes acomponent 612 which is disposed on a substrate 614. A dielectric layer616 is deposited over component 612 and substrate 614. Furthermore,components 608 and 610 are disposed on dielectric layer 616 ofsemiconductor wafer 600. A dielectric layer 606 is deposited overdielectric layer 616 and components 608 and 610. Moreover, semiconductorincludes a reflectance stop layer 602 which is deposited abovedielectric layer 606. Additionally, a dielectric layer 604 is depositedabove reflectance stop layer 602 of wafer 600. It should be appreciatedthat other embodiments of dielectric layers 604, 606, and 616, inaccordance with the present embodiment, include any type ofnon-conductive material (e.g., oxide, polymer, and the like). It shouldfurther be appreciated that embodiments of reflectance stop layer 602,in accordance with the present embodiment, include silicon oxy-nitride,amorphous silicon, and the like. Additionally, it should also beappreciated that embodiments of components 608-612, in accordance withthe present embodiment, include any type of conductive material (e.g.,aluminum, copper, silver, gold, and the like). After fabrication ofsemiconductor wafer 600, dielectric layers 604 and 606 are ready to beplanarized to a desired thickness using CMP machine 400 of FIGS. 4A and4B and the endpoint detection technique described above.

[0048] Referring now to FIG. 6B, which shows a determination of thethickness of dielectric layer 606 above components 608 and 610 usingincident light (e.g., incident light rays 618-622) during a CMP processof semiconductor wafer 600. Within the present embodiment, it isappreciated that a substantial amount of dielectric layer 604 has beenremoved during the CMP process. Furthermore, reflectance stop layer 602has been preferentially removed from above components 608 and 610 duringthe CMP process since high areas of topography (hills) are removedfaster than areas of low topography (valleys). As such, the remainingportions of reflectance stop layer 602 within the present embodiment actas absorption layers that block incident light reflection fromunderlying component 612 and substrate 614. Thus, reflected incidentlight is substantially obtained from components 608 and 610. As aresult, any changes in the reflectance of incident light during the CMPprocess is merely attributed to a change in the thickness of dielectriclayer 606 above components 608 and 610. Therefore, by providing a moreaccurate measurement of the thickness of dielectric layer 606 abovecomponents 608 and 610, the present embodiment provides more accurateendpoint detection during the CMP process. It should be appreciated thatendpoint detection of the present embodiment is set to start determiningthe thickness of dielectric layer 606 once reflectance stop layer 602has been polished away from above components 608 and 610 as shown inFIG. 6B.

[0049] Specifically, as CMP machine 400 polishes various layers ofsemiconductor wafer 600 as described above, transparent window slit 426passes underneath wafer 600. As such, incident light rays 618-622 passthrough window slit 426 and shine on wafer 600 as shown in FIG. 6B. As aresult, incident light ray 618 passes through dielectric layer 604 andis subsequently absorbed by reflectance stop layer 602. However,incident light rays 620 and 622 pass through dielectric layer 606,reflect off of components 608 and 610, respectively, and subsequentlypass through dielectric layer 606. Eventually, reflected incident lightrays 620 and 622 are used to determine the thickness of dielectric layer606 above components 608 and 610. Therefore, the present embodimentlimits what incident light rays 618-622 reflect off of within wafer 600.

[0050] Within the present embodiment, it should be appreciated that theif reflectance stop layer 602 is deposited too thin above dielectriclayer 606, it will not sufficiently suppress the reflection of incidentlight. As a result, the determination of the thickness of dielectriclayer 606 above components 608 and 610 will not be accurate during a CMPprocess. Therefore, it is important that a proper thickness ofreflectance stop layer 602 is deposited above dielectric layer 606,within the present embodiment. The examples previously described abovewith reference to FIGS. 5A and 5B illustrate this point.

DETAIL DESCRIPTION OF METHODS OF THE PRESENT INVENTION

[0051] With reference next to FIG. 7, a flowchart 700 in accordance withone embodiment of the present invention for providing more accurateendpoint detection during chemical mechanical polishing of semiconductorwafers. In step 702, in one embodiment of the present invention,components 504 and 506 of FIGS. 5A and 5B are patterned on substrate 502of semiconductor wafer 410. Within the present embodiment, it should beappreciated that during step 702, components 504 and 506 can bepatterned on surfaces other than substrate 502 (e.g., dielectric layer).

[0052] During step 704, within the present embodiment, reflectance stoplayers 508 and 510 are deposited and pattern above components 504 and506, respectively, of semiconductor wafer 410.

[0053] Within step 706 of FIG. 7, dielectric layer 512 is deposited overreflectance stop layers 508 and 510, components 504 and 506, andsubstrate 502 of semiconductor wafer 410.

[0054] In step 708, in the present embodiment, CMP machine 400 of FIGS.4A and 4B removes material from dielectric layer 512 by performing achemical mechanical polishing process on semiconductor wafer 410, asdescribed above.

[0055] Within step 710 of FIG. 7, the present embodiment determines thethickness of dielectric layer 512 of semiconductor wafer 410 usingincident light during the CMP process, as described above.

[0056] During step 712, the present embodiment determines whetherdielectric layer 512 of semiconductor wafer 410 has substantiallyachieved a desired thickness. If dielectric layer 512 of semiconductorwafer 410 has not substantially achieved the desired thickness, thepresent embodiment proceeds to step 708. If dielectric layer 512 ofsemiconductor wafer 410 has substantially achieved the desiredthickness, the present embodiment proceeds to step 714.

[0057] In step 714, CMP machine 400 of the present embodiment stopsperforming the chemical mechanical polishing process on dielectric layer512 of semiconductor wafer 410, as described above.

[0058] With reference now to FIG. 8, a flowchart 800 in accordance withanother embodiment of the present invention for providing more accurateendpoint detection during chemical mechanical polishing of semiconductorwafers. In step 802, in one embodiment of the present invention,components 608 and 610 of FIGS. 6A and 6B are patterned on dielectriclayer 616 of semiconductor wafer 600. Within the present embodiment, itshould be appreciated that during step 802, components 608 and 610 canbe patterned on surfaces other than dielectric layer 616 (e.g.,substrate 614).

[0059] Within step 804, dielectric layer 606 is deposited overdielectric layer 616 and components 608 and 610 of semiconductor wafer600 of the present embodiment.

[0060] During step 806, within the present embodiment, reflectance stoplayer 602 is deposited above dielectric layer 606 of semiconductor wafer600.

[0061] Within step 808 of FIG. 8, dielectric layer 604 is deposited overreflectance stop layer 602 of semiconductor wafer 600.

[0062] In step 810, in the present embodiment, CMP machine 400 of FIGS.4A and 4B removes material from dielectric layer 604, reflectance stoplayer 602, and dielectric layer 606 by performing a chemical mechanicalpolishing process on semiconductor wafer 600, as described above.

[0063] Within step 812 of FIG. 8, the present embodiment determines thethickness of dielectric layer 606 above components 608 and 610 ofsemiconductor wafer 600 by using incident light during the CMP process,as described above. It should be appreciated that endpoint detection ofthe present embodiment is set to start determining the thickness ofdielectric layer 606 once reflectance stop layer 602 has been polishedaway from above components 608 and 610 as shown in FIG. 6B.

[0064] During step 814, the present embodiment determines whetherdielectric layer 606 of semiconductor wafer 600 has substantiallyachieved a desired thickness above components 608 and 610. If dielectriclayer 606 of semiconductor wafer 600 has not substantially achieved thedesired thickness above components 608 and 610, the present embodimentproceeds to step 810. If dielectric layer 606 of semiconductor wafer 600has substantially achieved the desired thickness above components 608and 610, the present embodiment proceeds to step 816.

[0065] In step 816, CMP machine 400 of the present embodiment stopsperforming the chemical mechanical polishing process on semiconductorwafer 600, as described above.

[0066] Thus, the present invention provides a method and system thatprovides more accurate endpoint detection during a CMP process ofsemiconductor wafers. As a result of the present invention, an operatorof a CMP machine knows precisely when to stop a CMP process of asemiconductor wafer. Furthermore, the present invention enables theoperator of the CMP machine to know within a certain accuracy the film(e.g., dielectric layer) thickness remaining after the CMP process ofthe semiconductor wafer. Moreover, the present invention essentiallyeliminates excessive chemical mechanical polishing of the semiconductorwafer. As such, not as much dielectric material needs to be deposited onthe wafer in order to compensate for excessive chemical mechanicalpolishing of the semiconductor wafer. Therefore, the present inventionis able to reduce fabrication costs of semiconductor wafers.

[0067] The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the claims appended hereto and theirequivalents.

What is claimed is:
 1. A method for improving chemical mechanicalpolishing endpoint detection during planarization of a semiconductorwafer, said method comprising the step of: depositing a dielectric layerover a reflectance stop layer disposed above a component disposed on asemiconductor wafer, wherein said reflectance stop layer substantiallyreduces any light from reflecting off of said component during adetermination of the thickness of said dielectric layer using areflected signal of light.
 2. A method for improving chemical mechanicalpolishing endpoint detection during planarization of a semiconductorwafer as described in claim 1 wherein said step comprises: depositingsaid dielectric layer over said reflectance stop layer, wherein saidreflectance stop layer is comprised of a silicon oxy-nitride.
 3. Amethod for improving chemical mechanical polishing endpoint detectionduring planarization of a semiconductor wafer as described in claim 1wherein said step comprises: depositing said dielectric layer over saidreflectance stop layer, wherein said reflectance stop layer is comprisedof an amorphous silicon.
 4. A method for improving chemical mechanicalpolishing endpoint detection during planarization of a semiconductorwafer as described in claim 1 wherein said step comprises: depositingsaid dielectric layer over said reflectance stop layer disposed abovesaid component, wherein said component is comprised of a metal.
 5. Amethod for improving chemical mechanical polishing endpoint detectionduring planarization of a semiconductor wafer as described in claim 1wherein said step comprises: depositing said dielectric layer over saidreflectance stop layer, wherein said dielectric layer is comprised of anoxide.
 6. A method for improving chemical mechanical polishing endpointdetection during planarization of a semiconductor wafer as described inclaim 1 wherein said step comprises: depositing said dielectric layerover said reflectance stop layer disposed above said component, whereinsaid dielectric layer is comprised of an oxide and said component iscomprised of a metal.
 7. A method for improving chemical mechanicalpolishing endpoint detection during planarization of a semiconductorwafer as described in claim 1 wherein said step comprises: depositingsaid dielectric layer over said reflectance stop layer disposed abovesaid component, wherein said dielectric layer is comprised of an oxide,said reflectance stop layer is comprised of a silicon oxy-nitride andsaid component is comprised of a metal.
 8. A method for improvingchemical mechanical polishing endpoint detection during planarization ofa semiconductor wafer as described in claim 1 wherein said stepcomprises: depositing said dielectric layer over said reflectance stoplayer disposed above said component, wherein said dielectric layer iscomprised of an oxide, said reflectance stop layer is comprised of anamorphous silicon and said component is comprised of a metal.
 9. Amethod for improving chemical mechanical polishing endpoint detectionduring planarization of a semiconductor wafer, said method comprisingthe steps of: (a) depositing a reflectance stop layer above a componentdisposed on a semiconductor wafer, wherein said reflectance stop layersubstantially reduces any light from reflecting off of said component;(b) depositing a dielectric layer over said reflectance stop layer andsaid component; (c) removing material from said dielectric layerdisposed above said semiconductor wafer using a chemical mechanicalpolishing process; (d) determining the thickness of said dielectriclayer disposed above said semiconductor wafer using a reflected signalof light; and (e) in response to said dielectric layer substantiallyachieving a desired thickness, stopping said chemical mechanicalpolishing process of said semiconductor wafer.
 10. A method forimproving chemical mechanical polishing endpoint detection duringplanarization of a semiconductor wafer as described in claim 9 whereinsaid step (a) comprises: depositing said reflectance stop layer abovesaid component, wherein said reflectance stop layer is comprised of asilicon oxy-nitride.
 11. A method for improving chemical mechanicalpolishing endpoint detection during planarization of a semiconductorwafer as described in claim 9 wherein said step (a) comprises:depositing said reflectance stop layer above said component, whereinsaid reflectance stop layer is comprised of an amorphous silicon.
 12. Amethod for improving chemical mechanical polishing endpoint detectionduring planarization of a semiconductor wafer as described in claim 9wherein said step (a) comprises: depositing said reflectance stop layerabove said component, wherein said component is comprised of a metal.13. A method for improving chemical mechanical polishing endpointdetection during planarization of a semiconductor wafer as described inclaim 9 wherein said step (b) comprises: depositing said dielectriclayer over said reflectance stop layer and said component, wherein saiddielectric layer is comprised of an oxide.
 14. A device adapted forimproving chemical mechanical polishing endpoint detection duringplanarization of a semiconductor wafer, said device comprising: acomponent disposed on a semiconductor wafer; a reflectance stop layerdisposed above said component, wherein said reflectance stop layersubstantially reduces any light from reflecting off of said component;and a dielectric layer disposed over said reflectance stop layer andsaid component.
 15. A device of claim 14 adapted for improving chemicalmechanical polishing endpoint detection during planarization of asemiconductor wafer wherein said reflectance stop layer is a siliconoxy-nitride layer.
 16. A device of claim 14 adapted for improvingchemical mechanical polishing endpoint detection during planarization ofa semiconductor wafer wherein said reflectance stop layer is anamorphous silicon layer.
 17. A device of claim 14 adapted for improvingchemical mechanical polishing endpoint detection during planarization ofa semiconductor wafer wherein said component is a metal component.
 18. Adevice of claim 14 adapted for improving chemical mechanical polishingendpoint detection during planarization of a semiconductor wafer whereinsaid dielectric layer is an oxide layer.
 19. A method for improvingchemical mechanical polishing endpoint detection during planarization ofa semiconductor wafer, said method comprising the step of: depositing afirst dielectric layer above a reflectance stop layer disposed above asecond dielectric layer disposed over a component disposed on asemiconductor wafer, wherein said reflectance stop layer substantiallyreduces any light from reflecting off of other surfaces except saidcomponent during a determination of the thickness of said seconddielectric layer above said component using a reflected signal of light.20. A method for improving chemical mechanical polishing endpointdetection during planarization of a semiconductor wafer as described inclaim 19 wherein said step comprises: depositing said first dielectriclayer above said reflectance stop layer, wherein said reflectance stoplayer is comprised of a silicon oxy-nitride.
 21. A method for improvingchemical mechanical polishing endpoint detection during planarization ofa semiconductor wafer as described in claim 19 wherein said stepcomprises: depositing said first dielectric layer above said reflectancestop layer, wherein said reflectance stop layer is comprised of anamorphous silicon.
 22. A method for improving chemical mechanicalpolishing endpoint detection during planarization of a semiconductorwafer as described in claim 19 wherein said step comprises: depositingsaid first dielectric layer above said reflectance stop layer disposedabove said second dielectric layer disposed over said component, whereinsaid component is comprised of a metal.
 23. A method for improvingchemical mechanical polishing endpoint detection during planarization ofa semiconductor wafer as described in claim 19 wherein said stepcomprises: depositing said first dielectric layer above said reflectancestop layer, wherein said first dielectric layer is comprised of anoxide.
 24. A method for improving chemical mechanical polishing endpointdetection during planarization of a semiconductor wafer as described inclaim 19 wherein said step comprises: depositing said first dielectriclayer above said reflectance stop layer disposed above said seconddielectric layer, wherein said second dielectric layer is comprised ofan oxide.
 25. A method for improving chemical mechanical polishingendpoint detection during planarization of a semiconductor wafer asdescribed in claim 19 wherein said step comprises: depositing said firstdielectric layer above said reflectance stop layer disposed above saidsecond dielectric layer, wherein said first dielectric layer iscomprised of an oxide and said second dielectric layer is comprised ofan oxide.
 26. A method for improving chemical mechanical polishingendpoint detection during planarization of a semiconductor wafer, saidmethod comprising the steps of: (a) depositing a first dielectric layerover a component disposed on a semiconductor wafer; (b) depositing areflectance stop layer above said first dielectric layer; (c) depositinga second dielectric layer above said reflectance stop layer; (d)removing material from said second dielectric layer and said reflectancestop layer disposed above said semiconductor wafer using a chemicalmechanical polishing process, wherein said second dielectric layer andsaid reflectance stop layer subsequently are substantially removed fromabove said component; (e) determining the thickness of said firstdielectric layer above said component using a reflected signal of light,wherein said reflectance stop layer that remains substantially reducesany light from reflecting off of other surfaces except said component;and (f) in response to said first dielectric layer substantiallyachieving a desired thickness above said component, stopping saidchemical mechanical polishing process of said semiconductor wafer.
 27. Amethod for improving chemical mechanical polishing endpoint detectionduring planarization of a semiconductor wafer as described in claim 26wherein said step (b) comprises: depositing said reflectance stop layerabove said first dielectric layer, wherein said reflectance stop layeris comprised of a silicon oxy-nitride.
 28. A method for improvingchemical mechanical polishing endpoint detection during planarization ofa semiconductor wafer as described in claim 26 wherein said step (b)comprises: depositing said reflectance stop layer above said firstdielectric layer, wherein said reflectance stop layer is comprised of anamorphous silicon.
 29. A method for improving chemical mechanicalpolishing endpoint detection during planarization of a semiconductorwafer as described in claim 26 wherein said step (a) comprises:depositing said first dielectric layer over said component, wherein saidcomponent is comprised of a metal.
 30. A method for improving chemicalmechanical polishing endpoint detection during planarization of asemiconductor wafer as described in claim 26 wherein said step (a)comprises: depositing said first dielectric layer over said component,wherein said first dielectric layer is comprised of an oxide.
 31. Amethod for improving chemical mechanical polishing endpoint detectionduring planarization of a semiconductor wafer as described in claim 26wherein said step (c) comprises: depositing said second dielectric layerabove said reflectance stop layer, wherein said second dielectric layeris comprised of an oxide.